This invention is in the field of machines such as copying machines, facsimile machines, printers, or the like. A particular aspect of the invention relates to a sheet-reversing device for such machines.
FIG. 3 and FIG. 4 show one example of a conventional, prior art sheet-reversing device which comprises a main reversing roller 8a driven to rotate in a counterclockwise direction, a reverse roller 10a which is disposed upstream of the inlet sheet passage, and a reverse roller 9a which is disposed downstream of the same sheet passage. The reverse rollers 10a and 9a are in frictional contact with the peripheral surface of the main reversing roller 10 to be rotated thereby.
One mode of operation is called a "reverse mode." In this mode, the sheet is reversed such that it moves with its formerly trailing edge first. The reverse rollers 10a and 9a are spaced from each other as shown in FIG. 3. The sheet (not shown) is transported to the nip between the main reversing roller 8a and the reverse roller 10a, and then is fed to a switchback path 19a shown by the arrow D. After the trailing edge of the sheet passes the nip between the rollers 8a and 10a, the transporting direction of the sheet is changed to an opposite direction. Therefore, the sheet is pushed backward from the switchback path 19a and then is transported to the nip between the reverse roller 9a and the main reversing roller 8a as shown by the arrow E, and then is transported to a passage 18a as shown by the arrow B or to the other passage 17a as shown by the arrow F.
Another mode is called a "normal mode." In this mode, the sheet is not reversed; the reverse roller 10a and the reverse roller 9a are moved to a position as close as possible to each other while still contacting the main reversing roller 8a as shown in FIG. 4. Therefore, the sheet is not transported to the switchback path 19a shown by the arrow A, but is allowed to enter the nips between the reverse rollers 10a and 9a and the main reversing roller 8a. After that, the sheet is transported to either the direction B or the direction F.
Although the reversing or non-reversing of the sheet can be controlled by whether or not the sheet enters into the switchback path 19a as described above, there are disadvantages such as higher cost and structural complications, since the reverse roller 9a and 10a have to be moved between the position shown in FIG. 3 and that shown in FIG. 4 in order to change between the above-described two modes.
Further, as shown in FIG. 5, a sheet-reversing device is known in which the reverse roller 10b and the reverse roller 9b are in frictional contact with the main reverse roller 8b to be rotated thereby. The axes of rotation of rollers 10b and 9b are fixed with respect to each other.
When the sheet is to be reversed by this sheetreversing device, it enters into the sheet inlet path 14b shown by the arrow C as in the case of FIG. 3, and enters the nip between the rollers 8b and 10b to be transported to the switchback path 19b (the arrow D). The sheet then enters the nip between the rollers 8b and 9b with reversing. After that, the sheet is transported to either the passage 18b or the passage 17b (the arrow B or F).
When the sheet is not to be reversed, the sheet is transported to sheet path 15b (the arrow A) which branches from the sheet inlet path 14b, and then is directly transported to either the passage 17b or the passage 18b without passing through the sheet inlet path 14b and the switchback path 19b. The numeral 30 shows a pair of intermediate rollers disposed in the branched sheet path 15b.
Although there is no need for moving the reverse roller 10b and the reverse roller 9b in this device, the branching sheet path 15b has to be designed so as to bypass the roller 8b, 9b and can become undesirably long. Further, this device needs intermediate rollers, such as a pair of driving rollers 30, 30. Therefore, disadvantages such as higher cost and enlarging the whole structure of the sheet reversing mechanism still remain.
Accordingly, the invention is directed to arranging an apparatus having a sheet-reversing function in copying machines and other sheet-handling machines to enhance the desirable and suppress the undesirable characteristics thereof and to provide features not attained in the prior art.
In a nonlimiting example of an embodiment of the invention, a feed-in roller and a feed-out roller are frictionally driven by a main roller, and the axes of said rollers remain fixed. A normal sheet inlet guides a sheet to the nip between the feed-out roller and the main roller, and the sheet is transported from said nip to an outlet path without reversing. A reverse sheet inlet guides the sheet to the nip between the feed-in roller and the main roller, and the sheet is fed to a switchback path which extends from this nip in a direction away from those of the normal sheet inlet and the outlet path. After the trailing edge of the sheet clears the nip, the formerly trailing edge of the sheet is fed toward the nip between the main roller and the feed-out roller. The sheet is transported to the outlet path with reversing (trailing edge first). A sheet inlet switch is provided to change selectively between the normal sheet inlet and the reverse sheet inlet.
The apparatus can achieve a compact and inexpensive construction by eliminating the need to move the axes of the two reverse rollers and the need for a long sheet bypass path which has a pair of transporting rollers. Furthermore, the angle at which the sheet enters the nips between the rollers can be maintained constant to enhance the reliability of sheet transportation.
These and other features of the present invention will become apparent from the following detailed description of an embodiment thereof taken in conjunction with the accompanying drawings.